As systems, such as the multimedia entertainment, communications and diagnostic systems utilized by the automotive and aerospace industries, become more complex, a need arises for additional devices to communicate, either with each other or with a central controller or the like. Historically, these systems included dedicated wiring extending between the various devices in order to support communications therebetween. As systems have become more integrated and the communications requirements have been increased, the amount of dedicated wiring that would be required can quickly become excessively large, both in terms of the space required for the wiring and the cost of the wiring and the attendant installation.
As such, network systems have been developed to provide a common communications path between a plurality of network devices. In automotive and aerospace applications, for example, a network system can be utilized that includes a plurality of network devices located throughout the aircraft or vehicle to monitor various components and to collect diagnostic and status information. In this regard, diagnostic and status information relating to the strain, acceleration, pressure and/or temperature to which the various components of the automobile or aircraft are subjected may be collected and analyzed. By way of further example, a network bus architecture is currently being developed to support communications and the delivery of multimedia information to the occupants of a vehicle, such as an automobile, minivan, sports utility vehicle, aircraft, boat or the like. Advantageously, this network bus system would transport the audio signals, including streaming audio signals, produced by one or more network devices, such as a radio, a cassette tape player, a compact disc player or the like to selected speakers or headphone jacks throughout the vehicle. Similarly, the network bus may support voice and data communications with a cellular telephone carried by an occupant of the vehicle, as well as communications with a laptop computer, a handheld computing device or the like. In addition, the network bus may transmit video signals, including streaming video signals, from a television receiver, a videocassette recorder or other video source to one or more video monitors. Further, the network bus system may transport information related to diagnostic performance of the vehicle. Further, the network bus system may transmit sensor and actuator signals to and from devices such as drivetrain devices, passive restraint devices, crash avoidance devices, drive-by-wire devices, or the like.
In addition to the variety of network devices that are connected to a network bus, one or more controllers are also generally connected to the network bus for receiving data from the various devices and for sending commands to the devices. Among other things, these commands specify the manner in which the various devices are to function including the manner in which the various devices are to transmit information over the network bus. Additionally, the controller(s) can receive input from an operator, such as an occupant of the vehicle. This input can include, for example, an indication of the source(s) of the signals to be transmitted over the network bus as well as the destination of the signals.
An important aspect of network systems is the ability of the controller(s) to individually address either one or a subset of the network devices on the network system for either receiving information from or transmitting data to the network devices. For example, as described above, a typical network system may include several different types of network devices commonly connected to the same network bus. These devices may include multimedia devices, sensors, actuators, etc. all employed to provide certain functions within the system. In these network systems, the bus controller(s) must be able to address the network devices such that they perform their intended functions in the network system. In this regard, most network systems include an addressing scheme in which each of the network devices has an associated unique address. This unique address is used with the network system to identify and communicate with the network devices.
An important goal of many existing network systems and network systems currently in development is the ability to provide a flexible open framework system. Specifically, it is advantageous to provide a network system that allows for easy application of additional network devices to the current system or to remove network devices from the system. For example, in cases where network systems are used for diagnostic monitoring, it may be advantageous to allow for expansion of the network system by addition of new network devices, such as for example additional sensors or actuators. It may also be advantageous to allow for addition of portable or temporary network devices to the network system, such as diagnostic equipment, lap tops, etc., to perform diagnostics or other functions in the network. Similarly, in instances in which the network system includes a multimedia and/or communication component, it may be advantageous to allow systems such as cell phones, lap tops, game devices, etc. to be quickly and easily added or disconnected from the network system in a plug-n-play manner. An example would be the network system described above for use with vehicles, where the user may wish to connect their cell phone, laptop, multimedia player, etc. into the existing network system of the vehicle.
Although providing an open framework to allow expandability of the network system and/or plug-n-play capabilities is advantageous, there may be some difficulties implementing these features in current network systems. Specifically, as discussed above, many conventional network systems communicate with the various network devices using a unique address associated with the network device. These unique addresses are typically assigned during initial configuration of the network, at which time all network devices on the network bus receive their unique address. Further, during operation, the bus controller(s) typically uses a schedule, sometimes referred to as an operation or command schedule, to control the operation of the network system. The schedule contains a list of commands with predictable responses scheduled to communicate with the various network devices on the network using the addresses assigned to the network devices. As the addresses are typically assigned before communication in accordance with the schedule is began and the schedule typically only includes commands for the network devices currently connected to the network bus, subsequent network devices added to the network bus may not have an assigned address or be included in the schedule for communication on the network bus.
One solution to this problem is to preconfigure the added network device to have an assigned address. In this instance, the command schedule could also include commands that determine whether the network device is currently connected to the network bus and if so, perform desired communication with the added network device. However, this solution would require that addresses be set aside for a broad range of devices that could possibly be connected to the network bus and that the schedule include code for many network devices that may never be connected to the network bus. This may increase memory size and delay in the system. As such, a system is needed that allows for additional network devices to be added to the bus network in a plug-n-play fashion, while at the same time minimizing complexity and delay time.